考虑包晶相的Ti-Al合金定向凝固枝晶生长数值模拟

Numerical Simulation of Dendritic Growth During Directional Solidification Considering Peritectic Phase

考虑二元合金包晶反应和包晶转变过程,采用改进的CA方法建立了Ti-Al合金定向凝固过程中的组织演变数值计算模型,对液态金属冷却定向凝固过程中Ti-47.8Al(原子分数,%)合金包晶相的形成和具有不同优先生长方向的柱状晶的竞争生长进行了模拟。模拟了40 K/cm和80 K/cm两种温度梯度下合金的组织演化,并与相应的Ti-47Al-2Cr-2Nb合金定向凝固试验结果进行对比。结果表明,较之40 K/cm,温度梯度为80 K/cm时组织更快地进入稳定生长区,过渡区相对较短,而且柱状晶区晶粒的连续性更好,一次枝晶臂间距减小。

In the present paper, numerical models for microstructure evolution during directional solidification process of Ti-Al alloy were developed on the basis of modified cellular automaton （MCA） method, which took into account the peritectic reaction and peritectic transformation. The models were applied to the simulation of the formation ofpetitectic phase and the competitive growth of columnar dendrites with different preferred growth orientation during directional solidification process of Ti-47Al （atomic fraction, %） alloy using liquid metal cooling （LMC） method. Simulations of microstructure evolution during directional solidification were performed at the thermal gradient of 40 K/cm and 80 K/crn, and simulated results were compared with corresponding experiments of Ti-47Al-2Cr-2Nb. Simulated and experimental results show that columnar grains were well aligned along the growth direction from the bottom up to the upper part of the ingot at 80 K/cm, and compared with columnar grains obtained at the thermal gradient of 40 K/cm, the primary dendrite arm spacing decreased.